Can you use curves to make a pretzel?
Curves are probably not the best way to model this, you will have trouble getting smooth ends and squishing the overlapping parts with proper topology. Yet it is a totally acceptable method, if you are just looking for a quick and dirty solution.



Start with a bezier circle object, change all vertex handles to Aligned type, then erase one of the bottom quarters.

Move all but the bottom vertex to the side and duplicate them symmetrically around the X axis.

Connect the loose bottom vertex to the new half with F key.



Now extrude the two ends at the center making sure they extend in the correct direction, away from the opposite segment.



Spread both coinciding vertex at the center to the sides so the wont intersect, and move the corresponding handles slightly up or down to make both strings twist around each other, as if entangled.

Adjust both ends Z position so they stay resting above the ring.



Optionally use a Taper Object to get a smooth thickness progression along the string. You can also adjust per vertex thickness with the Radius property.